Yes, anything OEM is gonna be too expensive. Owners should be rewarded with less than or equal to average pricing when it comes to buying accessories.Cargo bags have the risk if not being 100% waterproof. Obviously a lot cheaper though. So if it is to use once or twice roof bag are fine, but for repeated use or heavier load rails and cargo box for sure.
Here's one that looks promisingWell in that regards the OEM rails are significantly cheaper than Thule and Yakima rails. But you can find cheaper stuff than OEM as well. I would say the OEM rails are smack in the middle. One thing to know about the OEM stuff is that they are slightly curved, so not as good to carry flat load.